Air conditioning system



March 22, 1938. w, ROESSLER 2,112,049

AIR CONDITIONING SYSTEM Filed May 5, 1936 Inventor":

Edward W502- slefi Patented Mar. 22, 1938 UNITED STATES AIR CONDITIONING SYSTEM Edward W. Rocssler, Nutley, N. J., assignor to General Electric Company, a corporation of New York Application May 5, 1936, Serial No. 77,949

v 11 Claims.

. My invention relates to systems for conditioning the air within auditoriums, rooms and other enclosures, and particularly to systems for cooling air and which include both temperature and humidity regulation.

During the summer months, when it is necessary to cool the air circulated through auditoriums, rooms and other enclosures in order to maintain the proper temperatures for maximum comfort, it is frequently desirable to use only a portion of the cooling surface available in a cooling coil. In such systems the cooling coil is utilized both to cool the air and to abstract moisture therefrom; the moisture which condenses on the cooling coil is collected and removed in any suitable manner. When the relative humidity of the air within a room is high, it may happen that the operation of the cooling coil will reduce the temperature of the air sufficiently to satisfy the requirements of the room thermostat before suflicient moisture has been abstracted from the air to satisfy the requirements of the room humidostat. In other words, it is desirable further to reduce the humidity after the temperature has been reduced to the desired value.

Accordingly, it is an object of my invention to provide an improved system for conditioning the air within an enclosure including a. cooling coil and an arrangement for varying the effective cooling surface of the coil dependent upon the temperature and humidity of the air in the enclosure.

Another object of my invention is to provide a system for cooling and dehumidifying the air within an enclosure including a cooling coil and an improved arrangement dependent upon the temperature and humidity of the air in the en-.

closure for varying the length of the portion of the coil containing superheated refrigerant vapor.

A further object of my invention is to provide a system for cooling the air within an enclosure including a cooling coil having a valve controlling the supply of cooling medium in response to the outlet temperature of the coil for maintaining a predetermined temperature of the cooling medium withdrawn from the coil and a device responsive to a condition of the air in the enclosure for modifying the operation of the valve to maintain a different predetermined temperature of the medium withdrawn from the coil.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For better understanding of my invention, ref-. erence may be had to the accompanying drawing, the single figure of which shows diagrammatically an air conditioning system embodying my invention.

Referring now to the drawing, I haveshown an air conditioning system comprising a casing 10 arranged to receive air from a room or enclosure to be conditioned through a duct l l opening into the room through a wall 9 and to receive fresh air from outside the room through a duct l2. Dampers I 3 and [4 are provided in the ducts II and I2, respectively, to control the amounts of fresh and room air admitted to the casing Ill. The fresh and room air mix in the casing l and the mixture passes through a filter I5 and. a cooling element I6 where the temperature and humidity thereof are reduced. The fresh air and the room air are drawn into the casing It! by operation of a fan or blower I! and the conditioned air is discharged into the room through a duct l8 passing through the wall 9.

The cooling element 16 comprises a sinuous coil l9- having a plurality of turns arranged in three banks Illa, I91), and 19c, each extending entirely across the casing 10 in the path of the air to be conditioned. This coil may be of any desired construction and is preferably of thetype provided with a plurality of fins to increase the eifective surface area thereof. Coil I9 is connected in the circuit of a mechanical refrigerating machine comprising a compressor 20, driven by an electric motor 21, which receives vaporized refrigerant from the coil I 9 through a conduit 22, compresses the refrigerant, andvdelivers the compressed refrigerant through a conduit 23 to a condenser 24. The compressed refrigerant in the condenser 24 is cooled and liquefied by air circulated thereover by a fan 25 driven by an electric motor 26 connected across the motor 2|. The liquid refrigerant flows into a receiver 21 and thence through an expansion valve 28 and a connection 29to the coil IS. The refrigerant is preferably admitted to the coil so that it flows through the banks of the coil in succession-in the opposite direction from that of the fiow of air'through the duct Ill. The air thus passes progressively from the least cold to the coldest bank of the coil.

The expansion valve 28 is of the thermostatically operated type well known in the art, it being operated in response to the temperature of the refrigerant withdrawn from the evaporator coil I9. when a vaporizable refrigerant is employed,

a-valve ofthis type may be set to maintain superheated the refrigerant vapor in any predetermined length or" the cooling coil. The valve 28 comprises a casing Bil divided by a partition 3i into an entrance chamber 32 and an outlet chamber A valve 30 arranged to seat in an opening in the partition 3i controls the passage of refrigerant from the inlet chamber to the outlet'chamber In order to provide thermostatic control of the valve 3 1, a diaphragm Ella. of the bellows type is sealed in the casing Bil to form a third chamber 358 at the end of the casing 28 re mote from the inlet chamber. The valve which is mounted on a rod Si is biased toward its closed position by a spring 38 and the force of the spring is opposed by the pressure of vapor in the chamber A bulb 39 containing a volatile liquid is secured adjacent the suction side of the coil l9 and determines the vapor pressure in the chamber to which it is connected by a tube ill; the pressure being varied in accordance with the temperature of the vapor withdrawn from the coil [19. An increase of the temperature of the vapor being withdrawn from the coil it will vaponze some of the liquid in the bulb 39 and increase the pressure inthe chamber This increase in pressure opposes the force of the spring 38 and opens the valve 3%, thereby admitting refrigerant to the coil H9. The operation of the EX- pansion valve 23 maintains a predetermined substantially constant temperature of the refrigerant withdrawn from the coil l9.

During normal operation of the cooling system shown, the temperature of the air in the room is regulated by a thermostat ll located in the room. This thermostat operates to control the connection between the motor 2!! and power supply lines 62 and Q3 and thereby determines the periods during which the compressor 2d shall operate to supply refrigerant to the coil it. The fan is operated only when the refrigerating machine is being operated.

The thermostat ll comprises a bimetallic strip td arranged to make contact with either one of two stationary contacts .15 and M5 depending upon the variation of the temperature in the room to be conditioned. When the temperature of the I air in the room rises to a predetermined maximum value, the strip Qt touches the contact 68 and closes a circuit from one side of a secondary coil ll of a transformer 48 through a line 59, the strip M, a connection 5t, to a coil at of a solenoid switch 52, and thence through a connection 53 and a line M to the other side of thesecondary ll. Coil Eli is thereby energized and raises an armature 55 of the switch 52 thereby raising two switch arms 56 and 5'8 to engage stationary contacts 5t and 59, respectively. The engagement of the switch arm 55 with the contact 58 closes a circuit including a connection Gil, switch arm 56, contact 58 and a connection 661, establishing a bypass around the bimetallic strip M and closing a holding circuit to maintain coil 5i energized from the transformer 58 even though the strip M should move away from the contact 55. The closing of the upper switch arm til establishes a circuit from the line t2 through a line 62, a connection F53, contact 59, arm 5?, and a line 6 3 to a coil 65 of a switch 66 and thence through a line bl to line d3. Energization of coil 65 raises an armature at of the switch 66 and closes the switch, thereby connecting lines 62 and 61 to leads 69 and ill, respectively, of motor 25 to start the motor and drive the compressor to. The fan motor 2b is connected across the leads 59 and m,

airaoce so that it is energized concurrently with the compressor motor.

The motor 25 will continue to operate and the refrigerating machine will supply refrigerant to the coil i9 until the temperature of the air within the room. to be conditioned has been decreased to a predetermined value whereupon the bimetallic strip 141 will engage the contact 65 and short-circuit the coil 55 through connection 59, strip a connection M and connection 53. The armature then falls into the position shown in the drawing and the arms 5% and El break contact with the contacts 58 and 59, respectively; this opens the circuit of coil 65, causing armature 68 to drop out and disconnect the motor M from the lines 62 and '51 to stop the operation of the compressor 2t and the fan 25. It will be noted that the arm 56 of the switch 52 in its drop-out position engages a contactv '92, the purpose of which will be hereinafter set forth.

When the humidity of the air in the room to be conditioned is high, it may happen that the thermostat it will be satisfied and will operate to stop the motor 2i before the humidity has been lowered sufficiently for comfort. It may be desirable in such a case to continue the operation of the coil H9 at a reduced rate .to remove further moisture from the air without greatly decreasing the temperature of the air passing through the duct. 1, therefore, provide an arrangement to modify the operation of the expansion valve and restrict the supply of refrigerant to the coil in the event that the humidity of the air in the room is still too high after the room thermostat has been satisfied. When the supply of refrigerant is thus restricted an increased percentage of the total coil length is filled with superheated refrigerant gas and the gas is withdrawn from the coil at a higher temperature. With the refrigerant flow restricted in this manner, the balance of heat transfer capacity between the coil and the compressor is changed so that a lower refrigerant pressure is maintained in the coil. The saturation temperature of the refrigerant is lower at the lower pressure, and the surface temperature of the coil is, therefore, lower in that portion of the coil in which the gas is not superheated. The dehumidi fication accomplished by this cold portion of the coil is increased as compared with dehumidification during the normal operation of that portion, but the total sensible heat removed by the coil from the air is reduced. ll arrange the device for modifying the operation of the expansion valve so that it is controlled in response to the humidity of the air in the enclosure to be conditioned.

The arrangement for modifying the operation of the expansion valve 23 comprises an expansible chamber or bellows E3 in communication with the valve operating chamber 35 through a tube it. By varying the volume of this second chamber the pressure in the chamber 3% is varied and, consequently, a different temperature of the bulb 39 will be required to produce the same movement of the valve. When the chamber i3 is compressed, a certain predetermined temperature of the bulb 39 will open the valve 33 and when the chamber i3 is expanded a higher temperature of the bulb is required to open the valve, for normal operation of the system in response to the thermostat ll the chamber i3 is held compressed and a minimum length of the coil i9 is maintained filled with superheated gaseous refrigerant. When only a portion of the coil i9 is to be used for cooling and dehumidifying the air, the

chamber I3 is allowed to expand, whereupon a greater length of the coil I8 is maintained filled with superheated gaseous refrigerant.

Any suitable arrangement may be provided for varying the volume of the bellows I3. In the construction illustrated, I have shown a second bellows I5 filled with air or other gas mounted in a casing I6 with the bellows I3 and connected at one end to the bellows I3 through a rigid member 11. The maximum volume of the bellows I3 is limited by a stop I8 formed in the walls of the casing I6 and the bellows I3 is biased to its expanded position by a compression spring I9. In order to compress the bellows I3, I provide a heating element 88 within the bellows I5 and energize the heating element to expand the air or other gas within the bellows I5. Whenever the thermostat 4| operates to start the motor 2| the circuit of the heater 88 is closed. This circuit may be traced from the line 62, through switch arm 51, a line 8|, an arm 82 of a solenoid switch 83 and a contact 84, to a line 85, and through heating element 88 and a connection 86 to line 43. Whenever the motor 2| is energized in response to operation of thermostat 4| the heating element is energized to compress bellows I3 and increase the pressure in the chamber 36 so that the thermostatic expansion valve 28 maintains a minimum temperature of the refrigerant withdrawn from the coil l8; that is, so that a minimum length of the coil I8 contains superheated vapor.

In order to maintain the desired humidity of the air in the room to be conditioned, I provide a humidostat 81. The humidostat 81 is arranged to operate the motor2| and continue the operation of the compressor 28 in the event that the humidity of the air in the enclosure is too high after the temperature conditions determined by the thermostat 4| have been satisfied. The humidostat 81 has no effect on the operation of the system unless the switch 52 operated by the thermostat 4| is in its drop-out position. In other words, control of the refrigerating machine in response to the room thermostat takes precedence over the control by the humidostat.

Should the humidity be too high after the minimum temperature determined by the thermostat 4| has been reached, a movable member 88 of humidostat 81 will be in engagement with a contact 88 and close a circuit from the secondary 41 of the transformer through arm 56 and contact I2, lines 88 and 9|, member 88, a connection 82,

a contact 93, a bimetallic strip 84, and a connection 85, to a coil 86 of the switch 83, and thence back to the secondary 41 through a line 81. The energization of the coil 86 raises a solenoid 98 of the switch 83 to lift arms 82 and 88 of the switch into engagement with contacts I88 and 8|, respectively. The engagement of arm 88 with contact |8| establishes a holding circuit for the coil 96 through a connection I82 to the line 88. The engagement of arm 82 with contact I88 closes a circuit from line 42 through a line I83, arm 82, connection 8| and line 64, to coil 65 and to line 43 through line 61, thereby energizing the coil 65 and closing the motor operating switch 66. Furthermore, when the arm 82 is raised, the circuit of the heating element 88 is broken and the bellows I3 expands and modifies the operation of the thermostatic expansion valve 28 to maintain the refrigerant withdrawn from the coil I8 at a higher temperature, as has been explained above. A major portion of the length of the search Room coil I8 is then maintained filled with superheated refrigerant vapor and a minimum length of the coil I8 is maintained at low temperature to abstract moisture from the air. Dehumidification of the air is thus continued with less cooling of the total volume of air circulated through the casing I8.

When the humidity is sufiiciently low, the member 88 of the humidostat 81 will engage a contact I84 to short-circuit the coil 86 through a connection I85 and thereby cause the armature 88 to drop out and de-energize the coil 65 to stop the motor 2|.

When the humidity of the air is extremely high, it may not be reduced sufficiently to satisfy the humidostat 81 before the temperature of the air becomes too low to be comfortable for the occupants of the room. In order to prevent excessive cooling of the air I provide a limit thermostat I86 responsive to room temperature. This thermostat comprises the bimetallic strip 94, the contact 93, and a second contact I81. The blmetallic strip 94 normally engages the contact 83. However, should the temperature of the air reach a predetermined minimum, which is the lowest temperature consistent with comfort, strip 94 will engage contact I81, short-circuiting the coil 86 through a connection I88 to open switch 83 and discontinue operation of the motor 2|.

It is probable that in the majority of air conditioning installations a substantial amount of heat is supplied to the enclosure to be conditioned from sources within that enclosure. For example, electric lights, motors, and other heat producing devices are often present in the room and heat is also produced in the room by the sun's rays entering through Windows. It is necessary that the heat from these internal sources be removed from the room before any temperature reduction below the temperature of the outdoor air can take place. In other words, a part of the capacity of the cooling system serves merely to overcome heat generated within the enclosure. Obviously, then a continuous circulation of a small amount of cooled air may be maintained without reducing the temperature of the air in the room; this circulation serving merely to balance the effect of the heat generated in the room. In the system which I have described above, it is possible to produce a substantial amount of dehumidification with only sufficient sensible cooling of the air circulated through the conditioner to offset the effect of the internal heat sources in the room and thus there results no reduction of the dry bulb temperature of the air in the room. It is apparent, therefore, that the low temperature limit thermostat would be operated only in rare cases.

It will be apparent from the foregoing that I have provided an air conditioning system including a simple and effective arrangement for regulating the temperature and humidity of an enclosure to be cooled, which makes possible the independent regulation of humidity after the room thermostat has been satisfied.

While I have disclosed a particular embodiment of my invention, various modifications will occur.

to those skilled in the art. I do not, therefore, desire my invention to be limited to the construction shown and described and I intend in the appended claims to cover all modifications thereof which do not depart from the spirit and scope of my invention.

What I claim as new anddesire to secure by Letters Patent of the United States is:

1. A system for conditioning the air within an enclosure including a duct communicating with said enclosure, a cooling coil arranged in said duct, means for supplying cooling medium to said coil and for withdrawing said medium from said coil, means responsive to the temperature of the medium withdrawn from said coil for maintaining a predetermined substantially constant temperature of said withdrawn medium, and means responsive to the humidity of the air in said enclosure and modifying the operation of said last-mentioned means for maintaining a predetermined different substantially constant temperature of said withdrawn medium.

2. A system for conditioning the air within an enclosure including a cooling coil, means for supplying liquid refrigerant to said coil and for withdrawing gaseous refrigerant from said coil, means responsive to the temperature of the refrigerant withdrawn from said coil for maintaining superheated the gaseous refrigerant in a predetermined length of said coil, and means responsive to the humidity of the air in said enclosure and modifying the operation of said last-mentioned means for maintaining superheated the gaseous refrigerant in a different predetermined length of said coil.

3. A system for conditioning the air within an enclosure including a duct communicating with said enclosure, a cooling coil arranged across said duct, means for supplying liquid refrigerant to said coil and for withdrawing gaseous refrigerant from said coil, means responsive to the temperature of the refrigerant withdrawn from said coil for maintaining superheated the gaseous refrigerant in a predetermined length of said coil, and means responsive to the humidity of the air in said enclosure and modifying the operation of said last-mentioned means for maintaining superheated the gaseous refrigerant in a shorter predetermined length of said coil.

4, A system for conditioning the air within an enclosure including a cooling coil, means for supplying cooling medium to said coil and for withdrawing cooling medium from said coil, means including a valve for controlling the supply of cooling medium to said coil, means responsive to the temperature of cooling medium withdrawn from said coil and actuating said valve for maintaining a predetermined substantially constant temperature of the cooling medium withdrawn from said coil, and means responsive to the humidity of the air in said enclosure and modifying the operation of said last-mentioned means for maintaining a different predetermined temperature of the cooling medium withdrawn from said coil.

5. A system for conditioning the air within an enclosure including a. cooling coil, means for supplying cooling medium to said coil and for withdrawing cooling medium from said coil, means including a valve for controlling the supply of cooling medium to said coil, means responsive to the temperature of cooling medium withdrawn from said coil and actuating said valve for maintaining a predetermined substantially constant temperature of the cooling medium withdrawn from said coil, means responsive to the humidity of the air in said enclosure and modifying the operation of said last-mentioned means for maintaining a difierent predetermined temperature of the cooling medium withdrawn from said coil, and means dependent upon a predetermined minimum temperature of the air within said enclosure for rendering said humidity responsive means ineffective.

6. A system for conditioning the air within an enclosure including a cooling coil, means for supplying cooling medium to said coil and for withdrawing cooling medium from said coil, means including a valve for controlling the supply of the cooling medium to said coil, means responsive to the temperature of the cooling medium withdrawn from said coil and including an expansible chamber and a bulb filled with a volatile liquid and communicating with said chamber for actuating said valve to maintain a predetermined substantially constant temperature of the cooling medium withdrawn from said coil, and means responsive to the humidity of the air in said enclosure and modifying the operation of said lastmentioned means by changing the pressure within said expansible chamber for maintaining a different predetermined temperature of the cooling medium withdrawn from said coil.

7. A system for conditioning the air within an enclosure including a cooling coil, means for supplying cooling medium to said coil and for withdrawing cooling medium from said coil, means including a valve for controlling the supply of the cooling medium to said coil, means responsive to the temperature of the cooling medium withdrawn from said coil and including an expansible chamber and a bulb filled with a volatile liquid and communicating with said chamber for actuating said valve to maintain a predetermined substantially constant temperature of the cooling medium withdrawn from said coil, means providing a second expansible chamber in communication with said first chamber, and means responsive to the humidity of the air in said enclosure and modifying the operation of said valve actuating means by changing the volume of said second chamber for maintaining a different predetermined temperature of the cooling medium withdrawn from said coil.

8. A system for conditioning the air within an enclosure including a cooling coil, means for supplying cooling medium to said coil and for withdrawing cooling medium from said coil, means including a valve for controlling the supply of the cooling medium to said coil, means responsive to the temperature of the cooling medium withdrawn from said coil and-including an expansible chamber and' a bulb filled with a volatile liquiddjjebmmunicating with said chamber for actuating said valve to maintain a predetermined substantially constant temperature of the cooling medium withdrawn from said coil, means for providing a second expansible chamber in communication with said first chamber, a

heating element arranged within said second chamber, means for energizing said heating element, and meansresponsive to the humidity of the air in said enclosure and varying the energization of said heating element to modify the operation of said valve actuating means by changing the volume of said second chamber for maintaining a different predetermined temperature of the cooling medium withdrawn from said coil.

9. A system for conditioning the air within an enclosure including a cooling coil, means for supplying cooling medium to said coil and for withdrawing cooling medium from said coil, means including a valve for controlling the supply of cooling medium to said coil, means responsive to the temperature of the cooling medium withdrawn from said coil and including an expansible chamber and a bulb filled with a volain said enclosure and maintaining said heating element de-energized to reduce the volume of said second chamber and modifying the operationof said valve actuating means for maintaining a difierent predetermined temperature of the cooling medium withdrawn from said coil.

10. A system for conditioning the air within an enclosure including a cooling element, means for supplying cooling medium to said element and for withdrawing said medium from said element, means dependent upon a predetermined maximum temperature of the air within said enclosure for actuating said cooling medium supplying means, means responsive to the temperature of the cooling medium withdrawn from said element and operable within a predetermined range of temperatures below said maximum temperature for maintaining a predetermined substantially constant temperature of said withdrawn medium during the operation of said cooling medium supplying means, and means responsive to the humidity of the air in said enclosure and actuating said cooling medium supplying means and modifying the operation of said temperature maintaining means for maintaining a predetermined difierent substantially constant temperature of said withdrawn medium during operation of said cooling medium supplying means, and means dependent upon a temperature in said enclosure below said predetermined range of temperatures for rendering ineffective said humidity responsive means.

11. A system for conditioning the air within an enclosure including a cooling element, means for supplying cooling medium to said element and for withdrawing said medium from said element,

means dependent upon a predetermined maximum temperature of the air within said enclosure for actuating said cooling medium supplying means, means responsive to the temperature of the cooling medium withdrawn from said element and operable within a predetermined range of temperatures below said maximum temperature for maintaining a predetermined substantially constant temperature of said withdrawn medium during the operation of said cooling medium supplying means, means responsive to the humidity of the air in said enclosure and operable when the temperature of said air is below said range of temperatures to actuate said cooling medium supplying means and modifying the operation of said temperature maintaining means for maintaining a predetermined difierent substantially constant temperature of said withdrawn-medium during operation of said cooling medium supplying means, and means dependent upon a predetermined minimum temperature of the air within said enclosure for rendering said humidity responsive 'means inefiective and for stopping the operation of said cooling medium supplying means. EDWARD W. ROESSLER'.

CERTIFICATE OF CORRECTION. Patent No. 2,112,0h9; 1 March 22, 19

\ EDWARD w. ROESSLER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1 second column, line 52, claim 8, for the word "in" read and; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5d day of, May, A. D. 1938.

Henry Van Arsdale, Acting Commissioner of Patents. 

